Phonograph pick-up



April 28, 1931. c. B. sAwYl-:R

I PHONOGRAPH PICK-UP Filed July 25, 1929 INVENTOR Charles Saver BY LIM/47 7776 Cd ATTORNEYS Patented lApr. 28, 1931 UNITED' s'ra'ras,l PATENTOFFICE CHARLES B. SAWYER, F CLEVELAND HEIGHTS, OHIO, ASSIGNOR, BY MESNEASSIGN- MENTS, TO THE CLEVELAND TRUST COMPANY, 0F CLEVELAND, HI, A.OORPQRA- PHONOGRAPH THICK-'UP application med :any 25, 1929. serial No.380,779.

This invention relates to new and useful mechanism for receivingvibrations from phonograph records and the like, and particularly theutilization of the piezoelectric V ei'ect of crystals, especially of theRochelle salt type, for converting such vibrations into electricalenergy.

The Rochelle salt crystal lends itself articularly to the conversion ofsound vi rations into electrical energy, since the electromotive forceis pro ortional to the pressure upon the crystal. very accurate responseor reproduction is obtained by arranging the crystal so that the actionof the grooves in the l5 phonograph record'upon the needle applies apressure upon the crystal which is proportional to the displacement ofthe grooves in the record.

One of the objects of the present invention is to provide such amechanism as may be utilized for reproducing the sounds recorded on v aphonograph record with exceptional fidelity.

Another object is to provide a mechanism in which the vibrationsreceived from the phonogra h record are converted into variations ofelectric potential which may be a plied to a thermionic amplifier ordirect y to a telephone receiver in order to enerate 0 sound wavesreproducing the origina sounds recorded on the phonograph record.

Another object of this invention is to provide a mechanism of greatmechanical ruggedness and endurance which will not be i harmfully aectedby mechanical shocks and stresses and which will not Wear out or changein quality with long use.

Another object of this invention is to produce a phonographicreproducing device 4" which will inherently eliminate a portion uof thescratching or rustling noises which are sometimes reproduced from therecord by mechanisms that have previously been produced. v

A further object of this invention is to provide a device having a verylarge response when played upona phonograph record so that acomparatively small amount-of amplification will be needed to give alarge response in the loud speaker or reproducer.

A still further object of the present invention is to provide a veryeconomical and eiicient utilization of the piezoelectric crystallinematerial.

Thesebeing among the objects of the present invention, the same consistof certain features of construction and combinations of parts to behereinafter described with reference to the accompanying drawin and thenclaimed, having the above and oter objects 1n view.

In the drawin which illustrates a suitable embodiment of t is invention,Figure 1 shows the ap lication of the sound reproducing mechanism to aphonograph;

Fig. 2 is an enlarged plan view of the conical base section of themechanism looking toward the needle-holding portion thereof;

Fi 3 is a side elevation of the crystalholding portion of thesound-reproducing mechanism; i

Fig. 4 is an enlarged perspective view of a cr stal;

ig. 5 is a cross-sectional view of the sound re reducing mechanism;

ig. 6 is a diagrammatic view showing the electrical hook-up for thesound reproducing mechanism showln the same connected with an amplifyingdevlce.

Referring to the accompanying drawings in which like numerals refer tolike parts throughout the several views, ythe sound reproducingmechanism 1 is shown in Fig. 1 as being attached to and supported -bythe goose-neck 2 of a phonograph tone arm 3. A needle 4, carried by themechanism 1, engages with the grooves of the phonograph record.

. The sound-reproducing element 1, as shown in Fig. 5, comprises a base6, a crystal holder 7 a nose-piece 8, and an electrlcal circuit whichwill be later described. The crystal holder 7 is of metal and embodies arelatively thin triangular-shaped web or vane 9 having a flangedcylindrical portion 1() at one end, which carries the needle 4, and alarge conical portion 11 at the other end thereof, which is seated in acorrespondingly shaped recess 12 formed in the base 6. A screw 13,carried by the base 6, is threaded into the conical end portion 11 ofthe lcrystal holder 7 to hold the cr stal holder in position in thebase. Triangu arly 'sha ed crystalline elements 14 and 15 of -Roc ellesalt, or other suitable crystalline m/aterial, are cemented to theopposite sidesfgfathe vane 9 with the ends thereof abutting against theconical end portion 11 and the flange 16 of the cylindrical end portion10. These crystalline elements 14 and 15 are also mounted undercompression to compensate for temperature chan es. Tinfoil electrodes 17and 18 are suita l attached to the outer faces of the crystallineelements 14 and 15 respectively and are connected together by aconnector wire 19 to form a single electrode. The base 6, being ofmetal, forms the other electrode.

The Acrystal holder is preferably enclosed by the nose-piece 8, which issecured to the base 6 by screws 20 and which has a flange 21 extendininto a counterbored portion 22 formed in t e base 6. The other end ofthe nose-piece 8 is tapered and engages a rubber or resilient ring 23,which is carried by tne cylindrical end portion 10 of the cr stal hold.-er. A screw 24 extending throng openings in the nose-piece 8 and ring 23is threaded into the end portion 10 to securely hold the needle 4 inposition.

The base 6 is also formed with a recess 25 at one end, whichtelescopically receives a resiliently mounted ring 26, that is employedto attach the base to the open end of the phonograph goose-neck 2.

The wire 19, which connects the pieces of tinfoil 17 and 18 to form asingle electrode, is provided with a leadwire 27 that extends throughthe base 6 and is connected to one terminal of a high resistancepotentiometer 28. The other terminal of the potentiometer 28 isconnected by a lead wire 29 to the base 6 which forms an electrode. Themovable arm 31 of the potentiometer 28 is connected to the controlmember of any suitable thermionic device 32. The thermionic device 32 isconnected by a lead Wire 33 to the-stationary terminal of thepotentiometer 28 and by a lead wire 34 to a suitable transformer 35,which is connected to a sound amplifying device 36, such as a loudspeaker. A battery 37, connected by lead wires 38 and 39 to thcpotentiometer 28 and transformer 35,completes the electrical circuit.

The operation of the device is as follows: The circular motion of therotating phonograph table causes the grooves in the record 5 to subjectthe needle 4 to lateral vibrationsat right angles to the groove, asindicated oy the double-headed arrow shown in Fig. `1 adjacent to theneedle 4. The needle 4 transmits these lateral vibrations to the crystalholder 7 of the mechanism, and the mechanism 1 and tone arm 3 as a wholetend to move back and forth in accordance with the lateral vibrations.This movement,

however, is resisted by the inertia of the arm 3 and mechanism 1 and, asa result of the force applied to the crystal holder 7 by the needle 4the vane 9 of the cr stal holder is subjected to bending stress ,whichcauses an alternate compression and tension of the crystalline elements14 and 15 at the opposite sides of the vane 8. The crystalline ele-*nents 14 and 15 are so oriented and carried by the crystal holder 7that the compression of one element and tension of the other elementtend to produce an electromotive force of the same polarity on the outersurface; that is to sa when pressure is exerted on the crystal older-.7,the crystalline element onv one side which is compressed develops apositive charge relative to the center and the crystalline element onthe other side, which is in tension, also develops a positive chargerelative to the center. Furthermore, when4 the lpressure tends to bendthe crystal holder init e-oppositedirection, the charge on thecrystalline elements, with respect to the center, is reversed andbecomes negative. Thus, when the needle is subjected to a vibrating oralternating pressure, an electromotive force is developed between theouter electrodes 14 and 15 and the vane 9 which forms the otherelectrode, which force is transmitted -through'the leads 27 and 29 tothe potentiometer 28, or in other words an electrostatic field isproduced at right angles to the axes of the crystalline elements.

Any desired portion of this electromotive force may be applied from theotentiometer to the control element of the t ermionic device 32,according to the position of the arm 31 of the potentiometer. Theelectromotive force is transmitted by the action of the thermionicdevice 32 through the transformer 35 to the loudspeaker or amplifier 36,vWhere it is converted into sound waves.

The electromotive force reproduced is of sufficient strength, so that ifsmall volume is required the output of the mechanism can be, applieddirectly toa sound reproducing device, such as a telephone receiver orsensitive loud speaker unit without the interposition of the thermionicdevice 32.

The resilient ring-23 surroundin the cylindricalend 10 of the crystalholder functions to prevent an excessivemovement of the crystal holder wich would tend to overload the crystalline elements, and also functionsto safeguard the mechanism against injury due to excessive mechanicalshocks. The cylindrical nose-piece 8 forms an enclosure for, the crystalholder and the attached crystalline elements and protects them fromexternal mechanical injury.

The mechanism illustrated is very sensitive to vibration applied to theneedle 1n a direction at right angles to the thin vane 9 of the crystalholder If, however, presure is exerted 1n directions more or less in theplane of the vane 9, such' as the scratches irregularities oftentimesoccuring in the bottom of the groove, there will be comparatively littlepressure exerted upon the c stelline elements, owing to the fact thatthe t 'n vane 9 is very stifi` and non-flexible in the direction of itswidedirection. Furthermore, both crystalline elements would becompressed or expanded at the same time by forces acting 10 in thisdirection and the electroniotive forces generated will therefore tend`to neutralize crystals and the nism for reproducing with exceptionalfidelity the ssounds recorded on a phonograph record.

It is to be understood that the shapes of particular methods andoperations setl fort are. for explanation and illustration only and that`formal changes can be made in the invention without departing from thespirit and substance of the broad invention, the scope o-fl which iscommensurate with the appended claims.

What I claim is: 1. In a piezo-electric device, in combination, asupport formin an inner electrode,

va pair of portions of piezo-electric material having outer electrodesconnected together, said portions being so secured to said support thateach portion constrains the movement of the other and so-arranged thatupon mechanical vibration of said support a relatively great pressure isapplied to said portions, whereby electrostatic potentials of high.intensity and like signs are produced on the outer electrodes, and apotential of opposite sign is produced on the inner electrode. y y

2. In a phonograph pick-up, 1n combination, a support and a (portion ofpiezo-elec tric material so oriente that when said portion is expandedor contracted by said support in the direction of its longitudinal 'axisit produces an electrostatic field at substantiallyright angles to saidaxis, said portion bein flexibly constrained so that when .a bendgingmoment is supplied an electrostatic field is produced.

3. In a phonograph pick-u in combination, a support, a ortion opiezo-electric material so oriente that when said portion is expanded orcontracted by said support in the direction of its longitudinal axis it.vice of a holder havin -field into sound waves.

y u 4. 'A piezo-electricfdevice including a portion of piezo-electricmaterial so oriented with respect to the cr stalline axes that whenalpres'sure is ap lie to said portion in the direction of itsongitudinal axis an electrostatic field is produced substantially atright angles to said axis, said portion being mounted under compression,whereby the natural period is raised and the effects of temperaturechanges are eliminated.

5. The combination in a' piezo-electric de spaced shoulders, a pair ofportions of piezo-electric material mounted etween said shoulders, and arecord engaging means carried by one end of said holder, the other endof said holder being of suflicient Wei ht as to be unaffected byvibration of sait? means Within the audible frequency range, saidportions of piezoelectric material bei mounted under` compression,wherebyrvi ration of said record engaging means causes application ofpressure to said portions in the direction of their longitudinal axes,and said portions being so arranged and oriented that an electrostaticfield will be set up substantially at right angles to said .longitudinalaxes.

6. In a phonograph pick-up, a relatively thin vane having shoulders at.the ends thereof, a pair of portions of piezo-electric material securedto said vane and mounted under compression between said shoulders, arecord engaging means carried by one end of said vane, and a base rigidlsupporting the other end of said vane, said use being of sufficientweight as to be unaffected by vibration of said means occurring withinthe audible frequency range, said portions of piezo-electric materialbeing so oriented that when they are expanded or contracted in thedirection of their longitudinal axes by the vibration of said vane theyproduce an electrostatic field at substantially right angles to saidaxes.

7. In a phonograph pick-up, a relatively thin vane having shoulders atthe ends thereof, a pair of portions of piezoelectric inaterial securedto said vane and mounted under compression between said shoulders, arecord engaging means carried by one end of said vane, a base rigidlysupporting the other end of said vane, said base being of sufficientweight as to be unaffected by vibration of said means occurring withinthe audible fre- .r

quency range, said portions of piezo-electric material being so orientedthat when they are expanded or contracted in the direction of theirlongitudinal axes by the vibration of said vane they produce anelectrostatic field charges relative to being sufiiciently held as to beunaffected by vibrations of said means occurring within the audiblefrequency range, said portions of piezo-electric material being sooriented that when they are alternately expanded and contracted by thevibrations of said record engaging means they produce an electromotiveforce, and means for converting said electromotive force into soundWaves. Y 9. In a phonograph pick-up, a relatively thin iiexible vanehaving shoul ers at its ends,

a record enga ing means carried by one end of said vane, t e other endofsaid vane being sufficiently held as not to be affected by Vvibrationsof said means, and portions of iezoelectric material secured to oppositesides of said vane and mounted under com ression between said shoulders,said portions eing so oriented that when the vane is subjected tovibrations within the audible frequency range they alternately expandand contract, and alternately develop positive and negative the centerthereof which produce an electromotive force, and means for' convertingsaid electromotive force into sound waves.

v 10. In a phonograph pick-up device, a relatively thin flexible vane, arecord engaging means carried by one end of said vane, the ther end ofsaid vane being sutliciently held as not to be aiected by the vibrationof said vane, and portions of piezo-electric material secured toopposite sides 45 of said vane and oriented to alternately-expand andcontract when said vanel is vibrated in the audible requency range andalternatelyl develop positive andnegative charges' relative to thecenter thereof which produce an' electromotive force, and means forconverting said electromotive force into sound waves.'

11. In -a phonograph 4pick-u device, n relatively thm vane having shouders at the ends thereof,'a pair of portions of piezoelectric materialsecured to said vane and extending between said shoulders a recordengaging means carried by one end of said vane, a base rigidlysupporting the other end of said vane, said -base being of sufficientweight as to be unaiected by vibration of said means occurring withinthe audible frequency range, said portions of piezo-electric materialbeing so oriented that when they are expanded or contracted in thedirection of their longitudinal axes -by the vibration of said vane theyproduce an electrostatic eld at substan-y

